From: Patrick Bellasi <patrick.bellasi@arm.com>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Steve Muckle <steve.muckle@linaro.org>,
Leo Yan <leo.yan@linaro.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
Todd Kjos <tkjos@google.com>,
Srinath Sridharan <srinathsr@google.com>,
Andres Oportus <andresoportus@google.com>,
Juri Lelli <juri.lelli@arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Chris Redpath <chris.redpath@arm.com>,
Robin Randhawa <robin.randhawa@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>
Subject: [RFC v2 4/8] sched/fair: add boosted CPU usage
Date: Thu, 27 Oct 2016 18:41:04 +0100 [thread overview]
Message-ID: <20161027174108.31139-5-patrick.bellasi@arm.com> (raw)
In-Reply-To: <20161027174108.31139-1-patrick.bellasi@arm.com>
The CPU utilization signal (cpu_rq(cpu)->cfs.avg.util_avg) is used by
the scheduler as an estimation of the overall bandwidth currently
allocated on a CPU. When the schedutil CPUFreq governor is in use, this
signal drives the selection of the Operating Performance Points (OPP)
required to accommodate all the workload allocated on that CPU.
A convenient way to boost the performance of tasks running on a CPU,
which is also little intrusive, is to boost the CPU utilization signal
each time it is used to select an OPP.
This patch introduces a new function:
boosted_cpu_util(cpu)
to return a boosted value for the usage of a specified CPU.
The margin added to the original usage is:
1. computed based on the "boosting strategy" in use
2. proportional to the system-wide boost value defined via the
provided user-space interface
The boosted signal is used by schedutil (transparently) each time it
requires an estimation of the capacity required by CFS tasks
which are currently RUNNABLE a CPU.
It's worth to notice that the RUNNABLE status is used to defined _when_
a CPU needs to be boosted. While _what_ we boost is the CPU utilization
which includes also the blocked utilization.
Currently SchedTune is available only for CONFIG_SMP system, thus we
have a single point of integration with schedutil which is provided by
the cfs_rq_util_change(cfs_rq) function which ultimately calls into:
kernel/sched/cpufreq_schedutil.c::sugov_get_util(util, max)
Each time a CFS utilization update is required, if SchedTune is compiled
in, we use the global boost value to update the CFS utilization required
by the CFS class.
Such a simple mechanism allows for example to use schedutil to mimics
the behaviors of other governors, i.e. performance (when boost=100% and
only while there are RUNNABLE tasks on that CPU).
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
---
kernel/sched/cpufreq_schedutil.c | 4 ++--
kernel/sched/fair.c | 36 ++++++++++++++++++++++++++++++++++++
kernel/sched/sched.h | 2 ++
3 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 69e0689..0382df7 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -148,12 +148,12 @@ static unsigned int get_next_freq(struct sugov_cpu *sg_cpu, unsigned long util,
static void sugov_get_util(unsigned long *util, unsigned long *max)
{
- struct rq *rq = this_rq();
unsigned long cfs_max;
cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());
- *util = min(rq->cfs.avg.util_avg, cfs_max);
+ *util = boosted_cpu_util(smp_processor_id());
+ *util = min(*util, cfs_max);
*max = cfs_max;
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fdacc29..26c3911 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5578,6 +5578,25 @@ schedtune_margin(unsigned long signal, unsigned int boost)
return margin;
}
+static inline unsigned long
+schedtune_cpu_margin(unsigned long util, int cpu)
+{
+ unsigned int boost = get_sysctl_sched_cfs_boost();
+
+ if (boost == 0)
+ return 0UL;
+
+ return schedtune_margin(util, boost);
+}
+
+#else /* CONFIG_SCHED_TUNE */
+
+static inline unsigned long
+schedtune_cpu_margin(unsigned long util, int cpu)
+{
+ return 0;
+}
+
#endif /* CONFIG_SCHED_TUNE */
/*
@@ -5614,6 +5633,23 @@ static int cpu_util(int cpu)
return (util >= capacity) ? capacity : util;
}
+unsigned long boosted_cpu_util(int cpu)
+{
+ unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
+ unsigned long capacity = capacity_orig_of(cpu);
+
+ /* Do not boost saturated utilizations */
+ if (util >= capacity)
+ return capacity;
+
+ /* Add margin to current CPU's capacity */
+ util += schedtune_cpu_margin(util, cpu);
+ if (util >= capacity)
+ return capacity;
+
+ return util;
+}
+
static inline int task_util(struct task_struct *p)
{
return p->se.avg.util_avg;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 055f935..fd85818 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1764,6 +1764,8 @@ static inline u64 irq_time_read(int cpu)
}
#endif /* CONFIG_IRQ_TIME_ACCOUNTING */
+unsigned long boosted_cpu_util(int cpu);
+
#ifdef CONFIG_CPU_FREQ
DECLARE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
--
2.10.1
next prev parent reply other threads:[~2016-10-27 17:43 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-27 17:41 [RFC v2 0/8] SchedTune: central, scheduler-driven, power-perfomance control Patrick Bellasi
2016-10-27 17:41 ` [RFC v2 1/8] sched/tune: add detailed documentation Patrick Bellasi
2016-11-04 9:46 ` Viresh Kumar
2016-11-08 10:53 ` Patrick Bellasi
2016-10-27 17:41 ` [RFC v2 2/8] sched/tune: add sysctl interface to define a boost value Patrick Bellasi
2016-10-27 17:41 ` [RFC v2 3/8] sched/fair: add function to convert boost value into "margin" Patrick Bellasi
2016-10-27 17:41 ` Patrick Bellasi [this message]
2016-10-27 17:41 ` [RFC v2 5/8] sched/tune: add initial support for CGroups based boosting Patrick Bellasi
2016-10-27 18:30 ` Tejun Heo
2016-10-27 20:14 ` Patrick Bellasi
2016-10-27 20:39 ` Tejun Heo
2016-10-27 22:34 ` Patrick Bellasi
2016-10-27 17:41 ` [RFC v2 6/8] sched/tune: compute and keep track of per CPU boost value Patrick Bellasi
2016-10-27 17:41 ` [RFC v2 7/8] sched/{fair,tune}: track RUNNABLE tasks impact on " Patrick Bellasi
2016-10-27 17:41 ` [RFC v2 8/8] sched/{fair,tune}: add support for negative boosting Patrick Bellasi
2016-10-27 20:58 ` [RFC v2 0/8] SchedTune: central, scheduler-driven, power-perfomance control Peter Zijlstra
2016-10-28 10:49 ` Patrick Bellasi
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